1. Field of the Invention
The invention relates to a method for the detection and/or determination of one or more components of the reaction between a specific binding protein and the corresponding bindable substance in an aqueous test sample, by applying the known binding affinity of such components for one another. Such components can be receptor proteins or immunochemical components, such as haptens, antigens or antibodies.
2. Description of the Prior Art, and Other Information
There are a large number of immunochemical methods known in which the presence of a certain immunological component is determined qualitatively and/or quantitatively by utilizing the mutual reactions between such components, such as the reaction between antigen and the antibody to that antigen.
In the study of such reactions for the demonstration and/or determination of the desired component, use may be made of aids, for example physical aids such as an electron microscope, or use may be made of a reagent which is provided with a marker or label which can be determined or demonstrated respectively in a lower concentration than the immunocomplex formed itself.
As examples of the category of qualitative immunochemical techniques there may be named the immunodiffusion method developed in 1948 by Ouchterlony and the variant thereof, immuno-electrophoresis, developed in 1953 by Grabar. The radial immunodiffusion method developed by Mancini in 1965 can be used quantitatively.
The immunodiffusion technique can be characterized as the placing of a thin layer of agar on a glass plate, after which two holes are made in the gel, a little distance apart. The test liquid with antigen is introduced into one of the holes, and an antiserum into the other. As a result of the diffusion of the two substances in the gel, these meet each other and form a visible precipitation line. Though this method is relatively simple, it does possess a number of disadvantages, in particular the fact that the diffusion lasts for some time and that the results usually only provide a qualitative indication. The other immunochemical techniques also have their drawbacks, which apart from specific disadvantages generally consist of too long a duration for the test, a low sensitivity and/or the provision of only qualitative indications.
In addition to these non-labelled immunochemical techniques, a number of labelled techniques have been developed with the passage of the years, amongst which there may be named the haemagglutination test in which one of the components is bound to the surface of erythrocytes; the immunofluorescence technique, in which one of the components is labelled with a fluorescent compound (fluorophore); the radio-immunological determination developed by Yalow and Berson about 1959, in which, instead of a fluorophore, a radio-active atom or radio-active group is used as marker; and the most recent technique of enzyme-immunological determination, about which the first publications appeared in 1971 from two groups working independently, namely the Swedish investigators Engvall and Perlmann and the Dutch Schuurs and van Weemen. This last-named determination is in principle analogous to the known radio-immunological determinations, but with the difference that an enzyme is used as label instead of radio-active labelling.
The much-used radio-immunological determination has indisputably great merit, but there are a number of substantial drawbacks associated with this method, such as the risk factor related to working with radio-active material, the high costs of reagents and apparatus, the poor stability of radio-active labelled reagents and the requirement that only qualified personnel be allowed to perform these determinations.
The enzyme-immunological determination method does not possess these disadvantages, but it is nevertheless desirable that new estimation techniques be developed which are even more sensitive, may be performed more rapidly, can be more readily automated and/or make it possible to estimate more than one immunocomponent at the same time.
Furthermore, there is a strong need for a reliable and practical assay for receptor proteins.